no-no

名词被禁止的东西，不准干的事

1. 不容许的事物;不能接受的事物;被禁止的东西
    If you say that something is a no-no, you think it is undesirable or unacceptable.

    e.g. We all know that cheating on our taxes is a no-no.
           我们都知道偷逃税是绝对不行的。